paraxial rays मीनिंग इन हिंदी

A "'paraxial ray "'is a ray which makes a small angle ( " ? " ) to the optical axis of the system, and lies close to the axis throughout the system.
For paraxial rays, the sphere gives the same results as the paraboloid or the exact fourth-order surface, as can be seen by Taylor-expanding the respective equations in terms of distance " y " from the axis ( the series for the paraboloid and the fourth-order surface are of course trivial ).